Madwed



3 Sheets-Sheet 1 March 10, 1964 A. MADWED DIE CASTING METHODS AND APPARATUS Filed May s1, 1962 HAD March l0, 1964 A'. MADWED DIE CASTING METHODS AND APPARATUS 5 Sheets-Sheet 2 Filed May 3l, 1962 INVENTOR. /lle/ Mada/ed BY )47'7'0/Q/EXS 3 Sheets-Sheet 3 March l0, 1964 A. MADWED DIE CASTING METHODS AND APPARATUS Filed May 31, 1962 S d www R8 N ow T7 @A ma m w r 1M (T F 2 1% fb .r/ 5 MY ,w T A B n 4 L -1 A u M f 4| n is? 5 Z @jf 0 /H/ 'qu u .LJ 5 7- 5] ////H/// /\v 0 Ban/m01 0 Z 4/45 94 Z 4 a a 75 5 4 z 2 o ,w Av A f /N wa v .M i A? N A A R 7l E f al 4 UnitedStates Patent O 3,123,875 DIE CASTING METHODS AND APPARATUS Albert Madwed, Bridgeport, Conn., assignor, by mesne assignments, to Automatic Casting Corporation, Bridgeport, Conn., a corporation of Connecticut Filed May 31, 1962, Ser. No. 198,916 Claims. (Cl. 22-70) The present invention relates to die casting methods and apparatus and more particularly to improvements in die casting whereby the problems arising from the freezing of molten metal in the nozzle of the injection device and/or the drippage of molten metal onto the die faces are avoided.

Conventional die casting machines comprise a pair of dies, one of which is movable and the other of which is mounted in stationary position on the machine and is provided with an opening through which the molten casting metal is injected. The molten metal is supplied by a pot on the machine and is injected into the die cavity, formed when the movable and stationary dies are brought together, by means of a plunger or piston which forces the molten metal through a gooseneck-type passage and through a nozzle at the end thereof into the die cavity. Metal is supplied to the gooseneck-type passage from a heated pot by a till port which is closed off by the plunger when the plunger starts down. After the plunger forces metal through the gooseneck and nozzle and into the die cavity, the plunger starts to return to its full up position and pulls a vacuum between the metal that remains in the gooseneck and the solidilied metal that remains in the filled die cavity. As soon as the ll port in the gooseneck chamber is opened, the atmospheric pressure above the molten metal in the pot forces the molten metal back into the gooseneck to ll the gooseneck and nozzle up to the metal which has previously remained in the die cavity. After the plunger returns to its full up position, the dies remain closed for a preset time to allow the casting to cool. After the preset time the dies open and the casting is pulled away from the nozzle. At this time in the cycle the molten metal in the nozzle gooseneck system tends to iiow back into the pot gooseneck system to reach a hydrostatic level. When the dies are fully opened the casting is ejected by means of knockout pins and a new cycle is begun.

It has been recognized for some time that although such automatic die casting machines are quick and efficient and have met with widespread commercial success, they do present one important problem which is due mainly to the fact that molten metal in the gooseneck returns to the nozzle and the casting after the plunger returns to the full up position because of the vacuum in the gooseneck and the opening of the lill port. In most dies there is cooling applied to the sprue section of the casting which is the section of the casting in direct communication with the nozzle. Because there is molten metal in the nozzle gooseneck system for most of the time that the casting is cooling, the sprue cooling is very critical. If too much cooling is applied the sprue of the casting freezes together with the metal in the nozzle and the casting will stick in the stationary die after the dies open. If the cooling is not enough, then the casting will not freeze or harden sufficiently and the tip of the sprue will be semi-molten and weak and generally will stick in the stationary die when the dies open, the remainder of the casting being withdrawn with the movable section of the die. Both these results of too much or too little cooling cause the casting operation to stop until the sprue and nozzle can be cleared. On the other hand, if the cooling is almost perfect, then when the movable section of the die opens and breaks the sprue from the molten metal ice in the nozzle, many times a drip of metal falls from the sprue while the movable die is retracted and is deposited on the face of the movable die and solidiiies so as to prevent complete closing of the dies when they are brought together for the next casting operation. Also some molten metal may run from the nozzle into the sprue portion of the stationary die and onto that die face so as to prevent complete closing of the dies when they are brought together for the next casting operation. It is almost impossible to get perfect cooling in the sprue section of the casting because it depends on temperature of molten metal, temperature of die, temperature of coolant, temperature of room, speed of operation and many other variables. Therefore compromises are generally made with conventional die casting machines and some problems with respect to clogging of the nozzle section or drippage onto the die faces are always encountered.

In view of the important problems or disadvantages resulting from drippage of the molten metal onto the die faces, many conventional die casting machines are provided with brushes which automatically sweep the die faces after ejection of each cast body. However, such brushes are not completely effective and their efiiciency must be constantly supervised. Also the period of time required for such brushing increases the length of the casting operation and substantially reduces the number of castings which may be made in an hours time.

It is therefore an yobject of this invention to provide an automatic die casting machine which prevents the molten metal in the gooseneck nozzle system from being in communication with the sprue of the casting for most of the cooling cycle and thus prevents or avoids the disadvantages attendant thereto, namely clogging of the nozzle section and/ or drippage of molten metal onto the die faces.

It is an advantage of this invention that cleaning brushes or the like are not required and that the efficiency of the machine is increased so that more castings may be produced per hour than heretofore possible.

It is another advantage of the invention that the degree of cooling or freezing of the casting is much less critical than with conventional die casting machines due to the absence of molten metal from the nozzle and upper portion of the gooseneck section during the cooling or freezing segment of the casting cycle. This leads to the further advantage that frequent stopping of the machine and cleaning of the nozzle are avoided.

These and other objects and advantages of this invention will be apparent to those skilled in the art in the light of the following description and the accompanying drawing in which:

FIGURE 1 is a side View of a segment of an automatic die casting machine according to the invention.

FIG. 2 is a side view of a segment of the machine illustrated by FIG. l and showing the molten metal being injected into the die cavity.

FIG. 3 is a side view corresponding to FIG. 2 but illustrating` the plunger in partially retracted position during solidification of the casting.

FIG. 4 is a side view corresponding to FIG. 2 but illustrating the plunger in fully retracted position and the dies being separated prior to ejection of the solidified casting.

FIG. 5 is a diagrammatic view of an automatic die casting machine mechanism according to one embodiment of the present invention.

As illustrated yby the drawings, Ithe present die casting machines comprise a furnace 1 having a heating chamber 2 `and ian opening 3y providing access for a gas flame or other heat-supplying means. Into; the heating chamber is mounted a vat 4 for maintaining the casting metal 5 in a molten condition. Though not essential -to the operation of the present apparatus, the vat is preferably separated into two receptacles, A and B, by means of partition 6, as illustrated, and the level of the molten metal in receptacle or pot A lis maintained constant by means of ladle 7 which is pivotally mounted on shaft 8 and which is yalso yslidably secured by pin 9 in slot 10 mounted on shaft 11 adjustably secured to the movable die block frame 12 by means of nuts i3. Any excess molten metal added to pot A by the ladle spills back over the partition into receptacle B.

Within pot A of the heating vat 4 is mounted metal injection mechanism 14 having -a shot cylinder 15, gooseneck 16 and provided at the upper end with a nozzle t7 communicating with the sprue -opening 18 of die 19 which is monuted in fixed position on the frame 20 of the machine. Plunger 21 is slidably mounted with- -in the shot cylinder- 15 and extends upward into a cylinder 22 mounted on the top frame of the machine. The cylinder 15 has a fill pont 14a communicating with the pot A and the molten metal therein to fill the cylinder i when the plunger is at its uppermost position. rIlhe top lof the plunger has mounted thereon piston 23 which is reciprocated in the shot cylinder by means of oil pressure alternatively exerted and exhausted through supply lines 24 and 24a which are connected to distributing valve 2.6, shown lin FIG. 5.

When the plunger is actuated downwardly or on forward stroke by exerting oil pressure in line 24 and exhausting through line 24a, it first closes the fill pont 14a and then .displaces the molten metal from the shot cylinder forcing it though gooseneck 16 and out the nozzle 17 into the die cavity as illustrated by lFIG. 2. This step occurs only when the dies are in engagement.

The movable die 27 tis mounted on die lblock 12 which has attached thereto plunger 23 which has on the opposite end a piston 29 slidably mounted within cylinder section 30, as illustrated in FIG. 5. The movable die 27 is moved towards yand locked against stationary die 19 by means of oil pressure exerted in cylinder 30, energizing plunger 2S and the die block. The die block and movable die are kept in perfect alignment with the stationary die by means of rods 31 on which the die block is slidably mounted by means of sleeves 32.

Associated with the movable die 27 is ejector bearing plate 33 having attached thereto knockout pins 34 and ejector rods 35. When the movable die is in engagement with the fixed die, the ejector plate is in the position shown in FIGS. 2 to 4 and the knockout pins are retracted so -as to be flush with the surface of the movable die. When the casting operation is completed and the movable ydie is retracted, as shown in FIG. 4, the ejector rods make contact with lan ejector block, segments shown 'as 319 in FIG. l, compressing springs 36 and forcing the knockout pins `against the casting 5a and `ejecting the casting from the core 37 on the movable die.

Also shown in FIG. l is `an auxiliary molten metal supply vat 49 which is suitably heated and which supplies additional mol-ten alloy metal as needed to receptacle B of main vat 4 by means of power-operated ladle 41 which is pivotally mounted on stationary arm 42 and on pistonoperated arm 43.

The operation of the clog-free, drip-free casting machines of this invention is similar to that of conventional Adie casting machines up to a point. For instance, each casting cycle begins when the `dies are separated or in open lposition and the injection plunger -is in the up position as illustrated by FIG. l. In conventional die casting, in the iirst phase of the casting operation, the dies are closed tand the plunger descends and fills the cavity. As soon as the molten metal in the dies, particularly in the gates, runners and/ or portions of the sprue, has had time to solidify, a matter of about a second in small castdngs, the plunger returns to its top fill port-opening position where it remains during the second phase of the cooling and article solidifying cycle, the length or" which depends upon the size and thickness of the articles being cast, a matter of four or five seconds with small castings, in order to permit the met-al in the article-forming cavities to solidify. It is at the beginning of the second phase of the cooling and ar-ticle solidifying operation where the present invention departs substantially from the conventional methods. According to the present invention, the plunger is not returned to its top position in which the fill port is opened but remains in Ian intermediate position keeping the fill port closed until the second phase of the casting operation is completed and the `dies are opened.

Referring to FIG. 5, a cycle is started when a casting made by the previous cycle and ejected onto chute 44 depresses pivoted arm 45 `and actuates switch 46 to set timer 47. The timer actuates distributing valve 48 which in turn energizes piston 29 within cylinder section 36' by means of oil pressure exerted through supply line 49 and exhausted through supply line 49a. The forward motion of the movable die -27 trips switch 50 and -actuates timer 51 `associated with distributing valve 26 for actuating the plunger 21.

Thus, when the dies are in engagement, yas illustrated by FIG. 2, the plunger makes its forward stroke and forces molten metal from the shot cylinder into the ydie cavity through gooseneck and nozzle 17. After the preset time, timer 51 again actuates distributing valve 26 and the plunger 21 begins its reverse stroke as the distributing valve converts exhaust line 24a to a power supply line and supply line 24 to an exhaust line, but according to the present invention the plunger is stopped from returning to the full up position as a lug 52 on the upper portion of the plunger trips switch 53 lactuating stop valve 54 which prevents the further exhaust of oi-l through line 24 and locks the plunger in the intermediate position a-a illustrated by FIGS. 3 and 4.

This is the most critical feature of the present apparatus since at this point of the casting cycle the die cavity has been filled with molten alloy metal and the return or reverse stroke of the plunger has created a vacuum in the gooseneck 16 of the injection mechanism whereby excess molten metal is drawn back from the nozzle 17 and from the upper portion of the gooseneck. Since the plunger is locked at position a-a of the shot cylinder 15, as illustrated by FIGS. 3 and 4, the fill port 14a in the wall of the injection cylinder is closed off so that the force of atmospheric pressure, exerted upon the molten metal in the pot A of the Vat 4, is prevented from destroying the vacuum in the gooseneck, which is what occurs with conventional die casting machines.

After a predetermined period for cooling and solidication of the casting, a few seconds or less, timer 47 again actuates distributing valve 48 causing the movable die 27 to be separated from the stationary die 19. The solidified casting 5a remains attached to the movable die section core 37, as illustrated by FIG. 4. As the movable die is withdrawn, it trips switch 55 which activates stop valve S4 releasing the same, thereby allowing the oil to exhaust from supply line 24 and causing the plunger to complete the reverse stroke as illustrated by FIG. 1 and shown by broken lines in FIG. 4, and opening the fill port 14a whereby additional molten metal is allowed to flow into the injection mechanism to compensate for the amount used up in the casting operation. As shown in FIG. l, the opening of fill port 14a allows the molten metal to fiow into the injection mechanism and to ll the gooseneck section until the level therein is equal to the level in pot A as shown in FIG. 1.

The level of the molten metal in the gooseneck is preferably kept high and as close to the opening in the nozzle as practical in order to reduce the amount of air present in the gooseneck and nozzle since excess amounts of air forced into the die cavity during the casting cycle result in defective castings containing air pockets and surface blemishes. This is preferably accomplished by means of the automatic ladling device illustrated.

Thus, as may be seen from FIG. l, the height or level of the molten metal in the gooseneck section corresponds with the level of the molten metal in pot A of the vat which in turn is controlled by the height of partition 6 separating from the vat into pots A and B.

As the movable die 27 and the die block 12 further retract, ladle 7 which had been in the lowered position submerged in the molten metal in pot B, as illustrated by the broken lines in FIG. l and as shown by FIG. 2, is pivoted on shaft 8 causing the spoon section of the ladle to be raised and causing the molten metal therein to be spilled over into pot A to compensate for the amount of molten metal used up in the casting operation.

At the same time the ejector rods 35 attached to the ejector plate 33 make contact with the ejector block 39 as shown in FIG. 1, causing the springs 36 to be depressed and the knockout pins 34 to pass through the movable die 27 and free the casting from the core 37. The solid casting 5a drops onto chute 44 causing the activation of switch 46 and the start of a new cycle.

It should be understood that the present invention is not limited to each of the features specifically discussed and illustrated, and alternative embodiments where desired will be obvious to those skilled in the art in the light of the foregoing description. The essential feature of the invention involves the provision of a die casting machine with suitable attachments whereby a vacuum is created in the gooseneck of the molten metal injection mechanism and the vacuum is kept intact until after the dies have been separated and the solidified casting has been withdrawn from the sprue opening of the stationary die.

While the aforementioned vacuum may be maintained in any desired manner such as by providing the fill port with a valve which is only opened when the dies are out of engagement or by controlling the withdrawal of the plunger whereby it moves at a reduced speed and enables the casting to be solidified and the die faces separated prior to the time that the plunger reaches the fill port, it is at present preferred to increase the efficiency of the apparatus by providing the plunger with a stop valve, as illustrated by the accompanying drawings, whereby the plunger quickly retracts to position a-a and is held in this position for a preset time to allow the casting in the article forming cavities to solidify and the die faces to separate before being returned to the full up position.

In conventional die casting machines, a vacuum is necessarily created in the injection mechanism when the plunger is withdrawn. However the withdrawal is instantaneous and complete and the vacuum is instantaneously destroyed once the plunger passes the opening or ll port connecting the supply vat and the injection cylinder since the molten metal in the supply vat is under atmospheric pressure. Thus the molten metal is sucked into the injection cylinder and the gooseneck and nozzle are completely filled at the time that the casting is solidified and the dies are separated. The Withdrawal of the sprue on the solidified casting from the sprue opening in the stationary die may have one of two consequences. If insufficient cooling was applied, then the sprue of the casting will be semi-molten and a small amount of molten metal may drip from the tip of the sprue or from the nozzle. In most cases this metal falls against the face of the movable die as it is withdrawn and solidifies thereon so as to prevent the die faces from coming into perfect contact during the next casting cycle. On the other hand, if too much cooling is applied, then even the residual molten metal in the nozzle in communication with the sprue opening will freeze and solidify together with the sprue of the casting whereby the tip of the sprue may break olf and stick in the sprue opening. Then the machine must be stopped and the solidified metal must be removed from the sprue opening and from the nozzle before the next cycle can be run.

These problems encountered with conventional die casting machines are completely overcome by the methods and apparatus of this invention since the vacuum created in the gooseneck section is maintained intact until after the casting is solidified and the dies are separated. There is no molten metal at or near the nozzle which can be caused to solidify or to drip into the sprue opening and, in fact, it has been found that the extreme tip of the sprue of the casting which is in contact with the hot nozzle and thus resists solidifying, is sucked back through the nozzle by the vacuum created in the gooseneck and the formed casting has a small hollow section where the tip of the sprue would ordinarily be. Periodic inspection of the castings therefore provides a quick and efficient check on whether the machine is performing as intended. The absence of molten metal from the nozzle and upper gooseneck section during the period of cooling and solidification of the casting renders the cooling step much less critical than with conventional machines. Thus although insufficient cooling might be applied any molten metal at the tip of the sprue will be sucked into the nozzle rather than being allowed to drip onto the die faces. On the other hand, there is no problem of cooling too much since there is no molten metal to freeze in the nozzle or upper gooseneck section.

While it is presently preferred, as illustrated, that the plunger and the movable die are activated by means of oil pressure and a distributing valve, it should be understood that various other actuating means obvious to those skilled in the art may be substituted if desired.

Variations and modifications may be made within the scope of the claims and portions of the improvements may be used without others.

-I claim:

1. A die casting machine for molten metal comprising a metal injection mechanism having a plunger and an injection cylinder and gooseneck which is adapted to be partially immersed in a pot of molten metal, said cylinder having a fill port which, when open, receives molten metal from the pot; a nozzle connected to said gooseneck; fixed and movable cavity-forming die members, the former having a sprue hole to communicate with said nozzle; means for moving said movable die member into and out of engagement with said fiXed die member; means for moving said plunger within said cylinder to close the fill port and cause molten metal to be injected into said die cavity through said gooseneck and nozzle land for retracting said plunger to such molten metal from the nozzle and adjacent portion of the gooseneck and create a vacuum until the fill port is uncovered whereby additional molten metal is allowed to fow therein; means for keeping said fill port closed and maintaining the vacuum in the nozzle and adjacent portion of the gooseneck until the molten metal injected into the die cavity has solidified and the die members have separated; means for automatically separating the movable die member from the xed die member; `and means operated coordinately with the separation of the die members for causing the lill port to be opened.

2. A die casting machine as defined in claim 1 in which the means operated coordinately with the separation of the die members includes means operated in response to the separating movement of the die members.

3. A die casting machine as defined in claim l in which the means for maintaining the fill port closed comprises means for arresting the plunger before it uncovers the fill port.

4. A die casting machine as defined in claim 3 in which the means operated coordinately with the separation of the die members includes means for rendering said plunger-arresting means inoperative.

5. A die casting machine -as defined in claim 3 in which there are means operated coordinately with the closing movement of the die members for rendering the said plunger-arresting means operative.

6. In the method of die casting in which molten metal is injected through a gooseneck and nozzle into a sprue hole of a closed cavity-forming die having fixed and movable die parts, the steps of injecting molten metal into the die cavity; withdrawing molten metal from the sprue hole, nozzle and adjacent portion of the gooseneck after portions of the casting metal in the die have solidified sufficiently to trap the metal in the articleforming cavities in the die; maintaining the molten metal so withdrawn while the metal in the article-forming cavities substantially solidilies; then separating the movable die part and casting from the fixed die part; and thereafter allowing the molten metal to rell the gooseneck preparatory to the next casting operation.

7. In the method of die casting in which molten metal is injected through a gooseneck and nozzle into a sprue hole of a closed cavity-forming die having lixed and movable die parts, the steps of injecting molten metal into the die cavity; withdrawing molten metal from the sprue hole, nozzle and adjacent portion of the gooseneck, after portions of the casting metal in the die have solidified suiciently to trap the metal in the article-forming cavities in the die, to create a vacuum between the solidified metal in the sprue hole and the molten metal remaining in the gooseneck; maintaining the said vacuum until the casting metal in the article-forming cavities in the die has substantially solidified; then separating the movable die part and casting from the ixed die part; and after said vacuum is broken by removal of the casting from the fixed die part, allowing the molten metal to refill the gooseneck preparatory to the next casting operation.

8. In the die casting process whereby molten casting metal is injected under pressure through a passage into the cavity between separable die parts and cooled to form a casting, the improvement which comprises applying a vacuum to said passage after the die cavity is filled, and after portions of the casting metal in the die have solidified to trap the metal in the article-forming cavities in the die and maintaining said vacuum until after the die parts are separated.

9. A die-casting process in which molten metal is injected through a nozzle and a sprue hole into the cavity of a pair of closed dies to form an article by operation of a plunger in a cylinder submerged in a pot of molten metal, the cylinder being connected to the nozzle by a gooseneck and receiving molten metal from the pot through a passage leading into its wall, the steps of closing the dies; operating the plunger to inject molten metal through the gooseneck and nozzle into the cavity formed c by the dies and at thel same time closing the passage from the pot to the cylinder; while the dies remain closed applying rapid return movement to the plunger while maintaining said passage closed to create and maintain until the dies separate a strong suction in the gooseneck to withdraw the molten metal from the sprue, the nozzle and adjacent part of the gooseneck and thereby prevent any molten rnetal from dripping from the sprue or the end of the nozzle or freezing in the nozzle and adjacent part of the gooseneck when the dies are separated and the casting is removed; separating the dies for the removal of the casting; and thereafter causing the passage between the pot and the cylinder to open and permit the cylinder and gooseneck to quickly refill for the next cycle of steps.

10. A die-casting process in which molten metal is injected through a nozzle and a sprue hole into the cavity of a pair of closed dies to form an article by operation of a plunger in a cylinder submerged in a pot of molten metal, the cylinder being connected to the nozzle by a gooseneck and receiving molten metal from the pot through a passage in its wall, the steps of closing the dies; operating the plunger to close said passage in the wall of the cylinder and then inject molten metal through the gooseneck nozzle into the die cavity; while the dies remain closed rapidly returning the plunger to a position in which the passage from the pot remains closed to create and maintain until the dies separate a strong suction in the gooseneck to withdraw the molten metal from the sprue, the nozzle and adjacent part of the gooseneck and thereby prevent any molten metal from dripping from the sprue or the end of the nozzle or freezing in the nozzle and adjacent part of the gooseneck when the dies are separated and the casting removed; separating the dies for the removal of the casting; and thereafter completing the return of the plunger to cause the passage in the wall of the cylinder to open and permit the cylinder and gooseneck to quickly rell for the next cycle of steps.

Bennett Dec. 1, 1953 Iagielski Oct. 2, 1962 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIG'N Patent Noo 3, 123,875 March lO, 1964 Albert Madwed lt is hereby certified that error appears in the above numbered patent requiring correction and that the Said Letters Patent should read as corrected below.

Column 3, line 14, for "monuted" read mounted line 30, for "though" read through column 5, line 4, strike out "rom"; column line 45, for "such" read suck column 8, line 25, after "gooseneck" insert and Signed and sealed this 7th day of July 1964,a

(SEAL) Attest:

ERNEST w; SWTDER EDWARD J. BRENNER insisting Officer Commissioner of Patents 

9. A DIE-CASTING PROCESS IN WHICH MOLTEN METAL IS INJECTED THROUGH A NOZZLE AND A SPRUE HOLE INTO THE CAVITY OF A PAIR OF CLOSED DIES TO FORM AN ARTICLE BY OPERATION OF A PLUNGER IN A CYLINDER SUBMERGED IN A POT OF MOLTEN METAL, THE CYLINDER BEING CONNECTED TO THE NOZZLE BY A GOOSENECK AND RECEIVING MOLTEN METAL FROM THE POT THROUGH A PASSAGE LEADING INTO ITS WALL, THE STEPS OF CLOSING THE DIES; OPERATING THE PLUNGER TO INJECT MOLTEN METAL THROUGH THE GOOSENECK AND NOZZLE INTO THE CAVITY FORMED BY THE DIES AND AT THE SAME TIME CLOSING THE PASSAGE FROM THE POT TO THE CYLINDER; WHILE THE DIES REMAIN CLOSED APPLYING RAPID RETURN MOVEMENT TO THE PLUNGER WHILE MAINTAINING SAID PASAGE CLOSED TO CREATE AND MAINTAIN UNTIL THE DIES SEPARATE A STRONG SUCTION IN THE GOOSENECK TO WITHDRAW THE MOLTEN METAL FROM THE SPRUE, THE NOZZLE AND ADJACENT PART OF THE GOOSENECK AND THEREBY PREVENT ANY MOLTEN METAL FROM DRIPPING FROM THE SPRUE OR THE 